Progesterone Cream, Flax Seed, and a Soy Supplements

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Dear OncoLink "Ask The Experts," My breast surgeon strongly recommends that I use topical natural progesterone cream, flax seed, and a soy supplement to decrease my risk of recurrent Stage IIB breast cancer. I am incorporating soy into my diet via soymilk and am adding flax seed to my soy breakfast cereal. I'm unsure, though, about how safe progesterone cream would be for me. I certainly want to do everything I can to prevent recurrence but I'm afraid the progesterone may "feed" any remaining cancer cells. What are your thoughts on someone with my history using progesterone cream?

Katrina Claghorn, MS, RD, Registered Dietitian at the Abramson Cancer Center of the University of Pennsylvania, responds:

There is currently too little information available on the effect of progesterone creams, flaxseed and soy on breast cancer. Phytoestrogens (plant estrogens) are present in soy foods and to a much lesser extent in flax seed. The assumption is that the plant estrogens may bind to the estrogen receptor sites, thus preventing the body's estrogen form binding and activating the cancer process. However, there is the possibility that phytoestrogens may act as triggers and actually increase cancer risk. Unfortunately the research is equivocal. The current recommendation is to limit your intake of foods containing plant estrogens to no more than 50 mg a day.

Topical use of progesterone cream is another issue that is has been investigated even less. Until there is more information on the effects of progesterone cream in women with a history of breast cancer, especially those that are PR+, we would advise against using these products.

Jul 10, 2013 - For men at high risk of biochemical recurrence after radical prostatectomy, daily consumption of a soy protein supplement is not associated with a reduction in the risk of recurrence, according to a study published in the July 10 issue of the Journal of the American Medical Association.